I have read no direct information about the Spark EV systems. But I believe that GM will use the same startup systems as in the Volt. The 12 VDC lead-acid battery is the main power for the control electronics and uses that DC power to startup and activate the larger lithium-ion traction battery. Then there is a DC to DC converter to keep the 12 VDC battery charged from the traction battery.
Maybe in the future the 12 VDC battery could be a smaller and lighter lithium-ion version to save weight.
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